In general, a fuel cell is called as a third-generation battery subsequent to a dry battery which is a first-generation battery and a storage battery which is a second-generation battery, and is a battery for converting chemical energy generated by the oxidation of a fuel directly into electrical energy.
Characteristics of the fuel cell are that reactants may be continuously supplied from the outside, electricity may be semi-permanently produced during the process in which reaction products are continuously removed out of the system, and the energy efficiency is very high because there is no loss generated in the mechanical conversion. Further, the fuel cells use various fuels such as fossil fuel, liquid fuel, and gas fuel, and are also divided into a low temperature type and a high temperature type according to the operating temperature.
Among them, a solid oxide fuel cell is a fuel cell which uses a solid oxide having ion conductivity as an electrolyte, and operates at the highest temperature (600 to 1,000° C.) among the existing fuel cells, has a simple structure compared to other fuel batteries because all the constituent elements are solid, has no problem with the loss, replenishment and corrosion of an electrolyte, and allows fuel to be easily supplied through direct internal reforming without a noble metal catalyst.
In addition, the solid oxide fuel cell also has an advantage in that combined heat and power generation using waste heat may be implemented because high-temperature gas is discharged. Due to these advantages, studies on the solid oxide fuel cell have been actively conducted.